Our overall objective is to understand the factors controlling oxygen delivery to the fetus-in-utero. This includes factors affecting placental respiratory gas transfer, control of fetal cardiac output and factors affecting oxygen exchange in fetal tissues. Individual studies include: 1) determine the role of hydrostatic pressures in maternal and fetal placental blood vessels in affecting transplacental water movements, 2) determine the role of osmotic pressures in maternal and fetal placental blood vessels in affecting transplacental water movements, 3) determine the relation of fetal extracellular fluid volume to blood volume, 4) determination of the placental diffusing capacity of carbon monoxide (CO) in the unanesthetized sheep, 5) determination of the relation of CO levels in muscle to that in blood for the mother and fetus, 6) determination of the effects of carbon monoxide hypoxia and hypoxic hypoxia on the fetus-in-utero, 7) determination of mean systemic pressure in a chronically prepared awake fetus, 8) development of a mathematical model of the time course of PO2 changes in the fetal circulation, 9) determination of effect of changing arterial PO2 on venous return, 10) determination of effect of umbilical cord clamping on venous return. BIBLIOGRAPHIC REFERENCES: Gusseck, D.J., P. Yuen and L.D. Longo. amino acid transport in placental slices. Mechanism of increased accumulation by prolonged preincubation. Biochem. Biophys. Acta 401: 278-284, 1975. Longo, L.D., E.P. Hill and G.G. Power. The factors affecting placental transfer of oxygen. In, Bioengineering in Medicine. J. Kline, Ed., 1975.